Firing mechanism for automatic and semi-automatic firearms



April 24, 1956 E. M. HARVEY FIRING MECHANISM FOR AUTOMATIC ANDSEMI-AUTOMATIC FIREARMS I5 Sheets-Sheet l a. k\/// Z!I Original FiledFeb. 11, 1949 I EurleM-Hurve r fi)-W%/%% April 24, 1956 E. M. HARVEYFIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS 5Sheets-Sheet 2 Original Filed Feb. 11, 1949 April 24, 1956 M HARVEY2,742,822

FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMS OriginalFiled Feb. 11; 1949 3 Sheets-Sheet 3 grwcm lom M g w ww 1 United Statesate-n t O FIRING MECHANISM FOR AUTOMATIC AND SEMI-AUTOMATIC FIREARMSEarle M. Harvey, Agawam, Mass, assignor to the United States of Americaas represented by the Secretary of War I 7 Claims. (Cl. 89-140) (Grantedunder Title 35, U. S. Code (1952), sec. 266) The invention described inthe specification and claims may be used by or for the Government forgovernmental purposes without the payment of any royalty thereon.

This invention relates to those firearms arranged to be selectivelyoperated in either semi-automatic or full automatic fire at the optionof the user and relates more specifically to an improved firingmechanism therefor.

The present application constitutes a division of my copendingapplication Serial No. 75,921 filed February 11, 1949, now Patent No.2,714,334.

One of the objects of this invention is to provide in an automatic andsemi-automatic firearm simple and reliable selector means adaptedto bereadily manipulated from one position to the other in either the open orclosed position of the bolt.

Another object of the present invention is to provide manual selectormeans for converting the operation of a firearm from semi-automatic toautomatic fire or vice versa which when once set in either of its twopositions will be positively yet releasably locked against accidentaldisplacement.

A further object of this invention is to provide in a firearm animproved fire control mechanism having latchmeans associated therewithfor retaining the bolt in the open recoiled position upon the cessationof automatic fire.

Still another object of this invention resides in the provision of animproved firing mechanism for an automatic and semi-automatic firearmwherein the bolt must be fully locked in battery position before thefiring pin can be actuated to discharge a cartridge.

A specific object of this invention is to provide in an automatic andsemi-automatic firearm an improved firing mechanism wherein the partsare so arranged that a single spring provides the functions of theconventional harnmer, trigger, and sear springs.

. The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawings in which:

Fig. 1 is a right side fragmentary view of the firearm showing theselector set for semi-automatic fire, the stock being cut away to revealthe firing mechanism of the present invention in a cocked positionpreparatory to pulling of the trigger;

- Fig. 2 is an enlarged longitudinal sectional view of Fig. l butshowing the selector set for full automatic fire;

--Fig. 3 is a cross-sectional longitudinal view showing the bolt andlocking block at the beginning of recoil;

Fig. 4 is a longitudinal sectional view showing the firing mechanism setfor full automatic fire and the bolt assembly at the beginning ofcounter-recoil movement about to be engaged by the bolt latch;

Fig. 5 is a perspective view of the trigger;

Fig. 6 is a perspective view of the selector;

Fig. 7 is a perspective view of the bolt latch;

Fig. 8 is a fragmentary detail view showing the hammer held in thecocked position by the sear during semiautomatic fire;

Fig. 9 is a fragmentary detail view showing the hammer held in thecocked position by the trigger and showing the selector cam set forsemi-automatic fire;

Fig. 10 is a view similar to Fig. 9 but showing the selector cam set forfull automatic fire;

Fig. 11 is a fragmentary detail view showing a moditied form of theselector cam; and

I Fig. 12 is a cross-sectional view taken along theline 1212 in Fig. 1showing the details of the selector and bolt latch mechanisms.

The firearm illustrated in Figs. 1 and 2 essentially comprises areceiver 5, a barrel 6 threadably secured to the forward end thereof, areciprocating bolt 7 having a locking block 8 associated therewith in amanner more fully described in my aforementioned copending application,and a trigger housing 9 suitably secured to the underside of receiver 5.

Bolt 7 as illustrated in Fig. 3 is provided with a longitudinal axialhole 10 having a counterbored portion 11 at the rear end thereof. Afiring pin 12 is slidably mounted in hole 10 and is provided with anenlarged cylindrical rear end 13 arranged to fit in counterbore 11. Apin 14 extends transversely through the rear end of bolt 7 and through acutaway portion 15 on the underside of the rear end 13 of firing pin 12thereby permitting limited longitudinal reciprocation thereof in bolt 7.A helical coil spring 16 is retained within counterbore 11 between thefront wall thereof and the shoulder formed by firing pin cylindricalrear end 13. Spring 16 normally biases firing pin 12 rearwardly in bolt7.

The forward end of locking block 8 terminates in a cylindrical portion17 arrangedto be pivotally retained in a suitable mating cut 18 formedin bolt 7. The underside of block 8 is cut away adjacent its rear endto'form a pair of spaced-apart locking shoulders 91, a side view of oneshoulder being shown in Figs. 2 and 3. A hole 19 is obliquely disposedin block 8 and extends forwardly therethrough to terminate in arectangular slot 20. A striker 21 is slidably disposed in hole 19 and isprovided with a rectangular front end 22 arranged to fit in slot 20. Theupper and lower forward edges of rectangular striker end 22 are beveledas shown at 23 and the lower beveled edge is arranged to be contacted bya similarly inclined shoulder 24 formed transversely across the rear endof bolt 7 for a purpose to be explained.

A camming lug 25' projecting laterally from a reciprocable operatingslide 26 is arranged to actuate locking block 8 between a raised lockedposition wherein rearward movement is prevented by a locking shoulder 27provided in receiver 5 and an unlocked position wherein block 8 islongitudinally aligned with bolt 7 for reciproeating movement inreceiver 5. In the full locked position of Fig. 2, firing pin 12 andstriker 21 are in longitudinal alignment while in the unlocked positionof Fig. 3, striker 21 is angularly inclineclwith respect to thelongitudinal axis of firing pin 12. It can therefore be readily seenthat as long as locking block 8 is not fully locked when in batteryposition, it is impossible to actuate firing pin 12 to discharge achambered cartridge 84.

A trigger 28 is pivotally mounted in housing 9 substantially midwaytherealong by means of a transverse pin 29 and comprises a conventionalarcuate finger piece 30 and an upwardly projecting body 31. The upperportion of trigger body 31 is offset to the right as best shown at 32 inFig. 5 and terminates at its upper end in a wedgeshaped lug 33projecting outwardly to the left for a pur- I pose to be hereinafterexplained.

A second transverse "pin 34 of slightly larger diameter than trigger pin'29 extends through the forward-end portion of trigger housing 9and'serves to pivotally mount a hammer thereto. It will be noted thatthe pivot point of such hammer 35 lies in a higher elevation than thepreviously mentioned pivot point of trigger 28 for a reason which willlater be more apparent. Hammer 35 comprises abody portion 36 and anintegral arm 37 projecting rearwardly from the upper 'end'thereof. Arm37 terminates in oppositely disposed lugs 38 and 39 as best shown by thedotted outline appearing in Fig. 3. The lower end of hammer bodyportion36 terminates in a downwardly depending extension 40 extendingbeyond hammer pin 34. A lug 42 formed on theright side of hammer 35 isarranged to lie in'abutment with a hammer lock mechanism, designatedgenerally bythe numeral 43, until such time asoperating slide26completes its counterreco1l movement as is fully described and explainedin a second copending application Serial No. 153,952, filed trigger 28is in its pulled position during'semiautomatic,

fire as will be later shown in more detail. A forwardly projectingarcuate portion 44 on sear 45 is arranged to extend into a rectangularopening 46 formed through trigger body 31 below the pivot point oftrigger 28. A transverse pin '47 extends through the walls of opening 46and sear arcuate portion 44 and thereby serves to pivotally secure sear45 to trigger 28. The upper end of sear 45 is provided with a forwardlyprojecting nose 48 arranged to retain hammer 35 in its cocked positionby engaging'over lug 38 thereon as will be hereinafter more fullydescribed. An arm 83 is arranged to project laterally -from the rightside of scar 45 for a purpose to be later shown.

-A'slot 49 is transversely formed through the lower rearportion of sear45 and serves to engage the rear loop 50 of a hammer spring 51. Thefront loop 93 of spring 51 is similarly engaged in a slot 41 providedthrough the forward portion of hammer extension 40., Such arrangementplaces hammer spring 51 in tension which therefore not only biaseshammer 35 in a clockwise direction but serves to return trigger 28 toa'pre-pulled position when released by the operator. Moreover, hammerspring 51 normally urges sear 45 forwardly against the rear surface oftrigger body 31 so as to be in position to engagehammer lug 38 when'trigger28 is in its pulled position. Sear 45 can, of course, be pivotedrearwardly about pin 47 against the'bias' of hammer spring 51 as will beclearly shown during the description of full automatic firing.Furthermore, since hammer spring 51 engages hammer 35 substantiallybelow the fulcrum thereof, the resulting lever armprovided byhammerbody. portion 36 isrelatively greater than that of conventionalconstructions wherein -a hammer spring is arranged to bear against ahammer above its point of rotation and be compressed during the cockingmovement thereof.

A U-shaped bolt retainer 52 is fixedly secured'at its rear end to therear end of trigger housing 9 and at its front end to receiver 5 therebyserving as a track for the underside of bolt 7 and locking block 8.A-selec'tor 53 is' rotatably mounted to the right side of retainer'52 bymeans of a transversepin member 61 and essentially comprises asubstantially rectangular body 54 and a finger piece 55 projectinglaterally therefrom adjacent the top portion thereof as best shown inFigs. 6 and 12. Selector body 54 is provided with a hole 56 extendingupwardly therein and arranged to accommodate a spring 57 and a detentplunger 58. A vertical slot 59 is also formed transversely through body54 so as to intersect hole 56. One end of pin 61 is slabbed on bothsides as shown at 60 in'Fig. 12, while the other end terminates in adepending lug 65. The slabbed portion 60-of pin 61 fits within verticalslot 59 and the adjacent cylindrical portion'63 is rotatably mounted ina suitablehole 64provided trans- '4 versely through the right side wallof retainer 52. Thus lug 65 isarranged to lie adjacent the inner side ofretainer 52. A suitable recess 62 is provided in the top surface ofslabbed portion 60 of pin 61 and is arranged to receive the detent endof plunger 58. As a result of such construction, selector 53 isreleasably secured to selector pin 61 so'that rotation of the formereffects similar rotation of the latter. The portion of selector body 54which projects upwardly beyond finger piece 55 is arranged to extendinto a suitablearcuate slit 67 provided in the underside of receiver 5.

Disassembly of selector 53 is achieved by inserting a drift 01" othersuitable tool up into vertical hole 56in selector body 54 and through avertical slot 66 formed along one side of slabbed portion 60 sothat'such tool contacts the bottom of plunger 58. Then by depressingplunger 58 against the bias of spring 57 and out of en gagement withrecess 62, selector 53 is thereby permitted to be removed from pin 61.

The side of selector body 54 which lies adjacent the outer wall surfaceof bolt retainer 52 is provided with a substantially rectangular recess68. The opposite lower corners thereof are arcuately extended. as bestshown at 69 in Fig. 6 so as to the receive the protruding reduced end 70of a transverse cylindrical pin 71 rotatably mounted in retainer 52.

Thus there is here provided positive means for releasably securingselector 53 in either of the two positions corresponding to theparticular one of corners 69 in which pin 71 is engaged. To changeselector 53 from one position to the other, it is merely necessary todepress selector body 54 against the bias of spring 57 by pressing downon finger piece 55. Since vertical slot 59 in body 54 is of greaterheight thanthe slabbed endportion 60 of pin 61, selector 53 will bedepressed sufficiently so that protruding end 70 of pin 71 will,disengage from one of arcuate corners 69 in rectangular recess 68. Thenselector 53 can be rotatedto the position desired and upon releasethereof pin end 70 will be automatically engaged with the other ofcorners 69'through the bias of spring 57.

Pin 71 also serves to rotatably mount a bolt latch 72 which comprises asubstantially H-shaped member having legs'73 and 74 connected'by a crossbar 75. The forward end of leg 74 is provided with an'offset dependinglug 76 having'a wedge-likelowerend 77 as best illustrated in Fig. 7.Legs 73 and 74 are each provided with a transverse hole 78in axialalignment with one another for passage therethrough of pin'71. The topof cross bar is provided with'a shallow arcuate cut 79 which permitspassagefor the underside of-locking block s. A coil spring 80 surroundspin 71 and one end thereof bears up against the underside of cross piece75 adjacent leg 74 of latch 72 while the other end of spring 80 isengaged in a slot '81 formed transversely through the left side wall ofbolt retainer 52. Consequently, spring '80 biases the rear ends of latchlegs 73 and74 upwardly in a clockwise direction so as to engage in frontof locking shoulders 91 and obstruct counterrecoil'movement-of lockingblock 8 and therefore of bolt 7 as well. However, when trigger 28 ispulled, a stud 82projecting from the right side thereof engageswedge-likejend 77 of latch lug 76 and rotates latch'72 in the oppositedirection against the bias of spring 80 whereupon-bolt 7 and lockingblock 8 are free to counterrecoil.

Referring now to Fig. 1 there is shown the firing mechanism of thisinvention in position to effect semi-automatic fire. Bolt 7 is in fullbattery position and locking block 8 has been cammed upwardly to projectin front of locking shoulder 27 on receiver 5. Manual retraction ofoperating slide 26 has broughtabout the cocked position of hammer 35which is then held cocked by engagement of lug39 thereon with lug33 ontrigger 28. Selector 53 has been rotated to the semi-automatic positionwherein selector lug 65 thereon is outof engagement with projectingarm'83 on sear 45.

mess-t natecartridge 84.

Operating slide 26 is driven to the rear in a manner conventional to gasoperated firearms. The initial recoil movement of slide 26 causescamming lug 25 thereon to unlockblock 8 from in front of receivershoulder 27. During this unlocking movement, the lower beveled edge 23of striker front end 22 contacts transverse shoulder 24 on the rear faceof bolt 7 thereby causing striker 21 to be cammed rearwardly in lockingblock 8 to the limit pemitted by the depth-of rectangular slot 20. Atthe same time, spring 16 biases firing pin 12 rear wardly to its cockedposition, Thus the rear end of striker 21 protrudes sufliciently to bestruck by hammer 35 during the next cycle of operation. 1 h

The continuing recoil movement of slide 26 carries .locking block 8' andbolt 7 rearwardly until the former :is arrested by a suitable buffer 85provided inthe rear end of receiver 5. During this recoil travel oflocking 'block 8, the underside thereof cams hammer 35 in acounter-clockwise direction whereupon hammer lug 38 :is forced past searnose 48 so as to pivot sear 45 rearwardly about pin 47. Thiscounter-clockwise movement of hammer 35 is finally halted by contactwith an upwardly projectingaabutment 86 formed on the right side oftrigger housing 9.

With trigger 28 still held in the pulled position due to the rapiditywith which the recoiling parts function, locking block 8 moves forwardlyin counter-recoil to ride off of hammer 35 which consequently begins torotate in the clockwise direction. Thereupon hammer lug 38 engages undersear nose 48 so that sear 45 holds hammer 35 in the cocked position ofFig. 8. When trigger 28 is finally released by the operator of thefirearm, sear nose 48 rides off of hammer lug 38 thereby permitting lug39 to engage beneath trigger lug 33 thus continuing to hold the hammercocked but this timeby trigger 28 as shown in Fig. 9. Then bypulling-trigger 28 again, another cycle of operation is initiated andthe firearm will operate semiautomatically as long as cartridges 84remain in magazine 88.

An alternative construction wherein bolt latch 72 is pivoted out of thepath of locking shoulder 91 on locking block 8 lies in the provision ofa depending lug 94 similar to lug 65'but' having a cam' portion 92thereon. When selector 53 is moved to the semi-automatic position, camportion 92 will engage wedge-like end 77 of bolt latch 72 and pivot suchlatch in a counterclockwise direction against the bias of spring 80. Asa result of this construction, stud 82 on trigger 28 will not be incontact with depending lug 76 of latch 72 thereby introducing adesirable decrease in the amount of pull required to actuate trigger 28.

Upon expenditure of the last round in magazine 88, a bolt stop lug 89 ona magazine follower 90 will spring up in front of bolt 7 thereby holdingit in the open position. When magazine 88 is removed from the firearm,bolt 7 and locking block 8 move forwardly slightly into engagement withbolt latch 72. Operating slide 26 must then be retracted slightly andtrigger 28 pulled so that upon release of slide 26, bolt 7 and lockingblock 8 will move into locked battery position as previously explained,and upon release of trigger 28, hammer 35 will engage therewith and beheld in the cocked position. Pulling of trigger 28 then serves toinitiate the semi-automatic firing cycle as outlined above.

When it is desired that the firearm operate as a fully automatic weapon,i. e., continue to fire as long as trigger 28 is held in thepulled'position and cartridges 84 are present in magazine 88, selector53 is rotated to the position of Fig. 2 through the procedure previouslydiscussed. Consequently, depending lug is rotated to engage sear arm 83thereby preventing clockwise movement thereof when trigger 28 is pulled.Thus when hammer 35 is rotated toward the cocked position by recoilinglocking block 8, sear 45 will be rendered inoperative and will notengage hammer lug 38 asin semi-automatic fire. Instead, hammer lockmechanism 43 holds hammer 35 cocked by engaging lug 42 thereon untilsuch time as operating slide 26 has attained its battery position.

Upon release of trigger 28, bolt latch 72 will rotate to obstruct thepath of movement of locking block 8 and consequently engage lockingshoulders 91 thereon to hold bolt 7 in the open position. When trigger28 is again pulled, bolt latch 72 will be pivoted to release lockingblock 8 and hammer lock mechanism 43 will release hammer 35 to initiateanother burst of automatic fire.

It can thus be readily appreciated by those skilled in the art thatthere is here provided a simple, compact and reliable selector mechanismwhich can be readily manipulated from either one of its two positions tothe other regardless of whether the bolt is in the open or closedposition. This feature is highly desirable in present day militarytactics inasmuch as the selector can be changed from automatic tosemi-automatic fire control during the open bolt position of the firearmthereby eliminating the usual loss of time involved in manually chargingthe gun for the initial shot.

in addition, the simple and positive means for rotatably mounting theselector mechanism to the firearm is also used to mount a boltlatchthereby utilizing a minimum number of parts in the firearm.

An additional reduction in the number of conventional parts normallyrequired in the type of firing mechanism herewith concerned isaccomplished by the unique arrangement of this'invention wherein thehammer spring serves not only tofunction the hammer but the trigger andsear as well. As a result, the conventional sear and trigger springs arenot here required. Moreover, by attaching the hammer spn'ng below thepivot point of the hammer, a far more rapid fall thereof is effected aspreviously explained. Thus, by increasing the speed with which thehammer can operate, a desirable increase in the rate of tire of theweapon can be readily obtained without the necessity for providing astronger hammer spring which in itself would serve to detract from themaximum rate of fire attainable by increasing the time required for boltrecoil.

- Iclaim:

1. In an automatic and semi-automatic firearm having a reciprocatingbolt and a locking block pivotally secured thereto for movementtherewith, a pivotal hammer mounted for movement between a cockedposition and a firing position, a pivotally mounted trigger arranged toengage and hold said hammer in its cocked position, a scar pivotallysecured to said trigger and arranged to engage and hold said hammer inits cocked position during such time as said trigger is in a pulledposition, a hammer spring arranged to be in tension when said hammer isengaged by either said sear or said trigger, selector means for pivotingsaid sear out of position to engage said hammer thereby producingautomatic fire when said trigger is pulled, pivotally mounted latchmeans for engaging the locking block during the initial forward movementthereof and thereby holding the bolt in an open position, said selectormeans arranged to be shifted between automatic and semi-automaticpositions in either the closed or open I portion having a vertical slotthere'through, a. cylindrical I selector pin rotatably secured in thefirearm, said pin having asIabbed endportion extending outwardly ofthe-firearrnand arranged tobe engaged insaid selector vertical slot, adetent slidably mounted in said selector'body portion and arranged to bereleasably engaged. with said slabbe'd end portion of saids'elector pinwhereby rotation of said selector effectscorresponding rotation of saidpin, a spring'arrangedto bias said detent. into said selector pinengagement, a depending'lugon' the other end'of said pinarranged-tomove'into and out of engagement with the sear'toeffect'pivoting' thereofas'said selector is rotated, means'for'releasably locking said selector and thereby said depending lug ineither a sear engaging or searjnonengaging position for respectivelyeffecting automatic ,or semiautoinatic fire, a bolt latchrotatablymounted in the firearm, spring means urging said'bolt latch intooperative position, and stud'me'ans onthe trigger for rotating saidlatchagainst the bias of said spring means and out of operativeposition whenthe trigger is pulled;

"5 The construction'define'din claim 4 wherein said means for releasablylocking said selector in either of its two'positions comprises,atransverse cylindrical pin fixedly secured in the firearmand "having-aprotruding end of smaller diameter, said selector having a rectan-'gular recess in the side thereof adjacent the firearm,'the lower cornersof said recess being arcuately formed "to engage said protruding end ofsaid cylindrical "pin, said detent spring being arranged to bias saidselector upwardly to maintain said cylindrical pin engagement, saidcylindrical pin-also being arranged to rotatably mount said bolt latch.1

6. In combination with a firearm having a triggerhousin g,-a triggerpivotally mounted in the housing for movement'b'et-weena pulledand'arreleasedposition, a hammer-rotatably mounted in the housing at apoint forwardly of: and inhigher elevation than the point oftrigger'pivot for movement between-a cocked and a firing position saidhammer having an integral footportion projecting beyond the point ofhammer rotation, a sear pivotally mounted to said trigger below thepivot point thereof for movement between a -hammer-retaining and mm lean rpp tinn a d a hammer tinsh ns- 1 0 we t saiflha n m POFF and.theother end connected to said sear above the pivot point thereof butbelow the pivot point of .said trigger, said spring being therebymounted in tension for'urging said sear to pivot into cocking engagementwith said hammer and for simultaneously urging said hammer to rotatetoward the firing position thereof while at the same time resistingpivotal movement of said trigger to the pulled position'thereof.

7. In combination with a firearm having a triggerrousing, a triggerpivotally mounted in the ,housing for movement between a pulled and areleased position, said trigger having a substantially rectangularopening therethrough below the pivot point thereof, ahammer rotatablymounted in the housing ata point forwardly of and in higher elevationthan the point of trigger pivot for movement between a cocked and afiring position, saidhammer having an integral foot portion projectingbeyond the point of hammer rotation to jforrn an angle with thelongitudinal axis of said hammena sear having a forwardly projecting'arcuate'base portion and an upwardly extending hammer-engaging portion,said arcuate base being pivotally secured in said rectangular opening ofsaid trigger with said upwardly extending seat portion disposed behindsaid trigger for pivotal movement into and out of cocking-engagementwith said hammer, and a hammer spring having a forwardly projecting loopportion connectedto said hammerfoot portion and a rearwardly projectingloop portion connected to said sear between the pivot point thereof andthat of said trigger, said spring being ,mounted under tension forurging said hammer to rotate toward the firing position andsimultaneously'urging said'sear to pivot intohammer-engaging positionwhile at the same time resisting the pulling of said trigger to efiectthe return thereof to the pre-fired position when released.

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